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    <script>
    //统计数组中元素出现的次数
    /*[1,2,3,1,1,1,2,2,3,3,4]
    1出现的次数 4
    2出现的次数 3
    3出现的次数 3
    4出现的次数 1 */
    var arr = [1,2,3,1,1,1,2,2,3,3,4];
    var res = arr.reduce(function(pre, cur){
        if(cur in pre){
            pre[cur] += 1;
        }else {
            pre[cur] = 1;
        }
        return pre;
    },{})
    for (var key in res){
        console.log(key + '出现的次数' + res[key]);
        
    }
    </script>
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